Cancer cells display unusually glycosylated cell surfaces that are often correlated to cancer behavior. However, the question of why and when cancer cells exhibit aberrant glycosylation remains largely unanswered because current analytical tools cannot observe rapid glycosylation changes. I plan to develop an imaging platform able to reveal cancer glycosylation with both spatial and temporal resolution. The proposed strategy will use the chemical reaction of a cyclooctyne probe (copper-free click reaction) with an unnatural cell surface azide-labeled sugar to attach a visualizing agent to the cancer cell. The innovation of the new probes is sensitivity and specificity for azide imaging; the probes were designed to only form the visualizing agent after reaction with azide. This will increase imaging sensitivity because off-target binding and residual probe will not contribute to background noise. Two generations of cyclooctyne probes will be developed with two distinct visualizing agents: a fluorescent smart probe (Aim 1) and a chemiluminescent probe (Aim 2). The fluorescent cyclooctyne probe will be used to quantify sialic acid content on the surface of Chinese hamster ovary cells (Aim 3). The chemiluminescent cyclooctyne probe will be used to measure the effectiveness of a known sialyl transferase inhibitor with potential as an anti-cancer metastasis agent. The long-term goal of this project is to develop an imaging platform capable of elucidating how glycosylation affects cancer behavior in model organisms.